1. Field of Invention
The present invention relates to a voice recognition method and a system for use with a telephone dialing, and more particularly to a callflow dialog that automatically transfers between different dialing modes.
2. Description of the Prior Art
A conventional telephone network switch has a timeout period, i.e. Receiver Off Hook ("ROH timer") to indicate when a telephone receiver is placed offhook and there is no activity on that line. Since this switch considers dialing to be the only detectable "activity", a voice dialog between a caller and a voice recognition system does not normally disengage the ROH timer. Therefore, callflow dialogs prior to connection must typically be constructed to be complete before the ROH timeout occurs, i.e. within 10-20 seconds after the handset is taken offhook. This significantly constrains interaction options.
A conventional Voice Activated Dialing (VAD) service, such as Bell Atlantic's Easy Voice.TM., uses an in-band switch protocol such as a Network Facility Access (NFA) protocol or a Proxy protocol. Both of these protocols provide the capability to connect an Intelligent Peripheral (IP) that performs voice recognition for enhanced voice-enabled services. These in-band protocols use the seize signal, the wink signal, and dual tone multiple frequency (DTMF) tones to transmit call setup and control information. The system has a switch interface which interprets two bit patterns: onhook and offhook. These patterns correspond to "00" for an offhook state and "11" for an onhook state. The VAD switch interface distinguishes a "seize" signal from the switch as a transition from the onhook to the offhook states; "wink" is a transition from the offhook to the onhook state and then back to the offhook state.
The following description discusses the NFA/Proxy protocol related problem of the above VAD application in particular, however, the problem and solution should apply to any switch protocol that uses an ROH timer. VAD callflows for the VAD system above may be initiated in the "implicit" mode. The caller has generally three options: (1) manually dial a number using DTMF tones, (2) speak a name (e.g., "John Smith") contained in a VAD directory, and have the VAD dial the corresponding number that is stored in the VAD directory, or (3) speak the directory management command (e.g., "directory") or dial the corresponding star-code command (e.g. "*44") to get into the explicit directory management mode.
The NFA and Proxy switch protocols are similar. They both provide two modes of operation. One mode is an implicit mode which occurs automatically when a provisioned caller line is taken offhook. During the implicit mode a DTMF receiver is enabled only to listen for DTMF signals. In addition, the ROH timer is also enabled. Another mode is an explicit mode which conventionally occurs when a star code, for example "*XX" ("X" representing a DTMF numerical signal), is entered via DTMF signals. Once the star code is entered and transition to the explicit mode is completed, the DTMF receiver and the ROH timer are disabled. Thus, the switch neither listen for the DTMF signals nor disconnects the line when the ROH timer expires. Instead, the control of the line is transferred to the IP. Such IP may have a voice recognition detector and a DTMF signal receiver.
Both the NFA and Proxy protocol transmits a two-digit code during the call setup connection to the IP. By convention, a service code of "00" indicates the implicit mode of NFA, "01" indicates the implicit mode of Proxy, and "44" indicates the explicit mode for either protocol. The IP interprets the service code in order to determine the prompts and call flow options that will be provided to the caller. For example, when a caller line goes offhook, the IP receives a call setup with an implicit service code (i.e., "00" or "01") and the IP provides a "beep" prompt to the caller. If the caller dials "*44" to switch to an explicit directory management call, the implicit call is disconnected; the IP receives a new call setup from the switch with the "*44" service code; and the IP provides a prompt of directory management options. The IP handles this explicit directory management session as a separate call from the initiating implicit session.
One of the significant differences between the explicit and implicit modes is that the implicit mode has a short time period (10-20 seconds configured as the ROH timer) before a call is disconnected. Thus, there is a set time limit for the implicit mode to dial before a disconnect. The explicit mode, however, operates indefinitely with no timeout for automatic disconnect.
U.S. Pat. No. 5,452,340 to Engelbeck et al. ("Engelbeck") describes a method of interface between a voice activated dialing system and a user. The Engelbeck patent provides an option for the interface to add, remove, or change a name and corresponding telephone number in a telephone directory during the process of initiating a telephone call. However, the Engelbeck patent does not address any issues resulting from time constraints, such as the ROH timer.